Method and apparatus for tension control



Dec. 13,1927. 1,652,299

C. E. CARPENTER METHOD AND APPARATUS FOR TENSION CONTROL Filed Oct. 18,1921 s Shets-Sheet 1 ULp Mu (3W I A TTORNEY Dec. 13,1927. v 1,652,299

C. E. CARPENTER METHOD AND APPARATUS FOR TENSION CONTROL Filed Oct. 18,1921 3 Sheetsheet 2 Dec. '13, 1927. 1,652,299

c. E. CARPENTER METHOD AND APPARATUS FOR TENSION-CONTROL Filed 001;. 18.1921 :5 Shets-Sheet 5 ATTORNEY Patented Dec. 13, 1927.

PATENT OFFICE.

. UNITED STATES CHARLES E. CARPENTER, NEW YORK, N. Y.

METHOD AN D APPARATUS FOR TENSION CONTROL.

Application filed October 18, 1921. Serial N0. 508,547.

but is generally useful where it is desirable to maintain tension onmoving web or strand-like material.

In maintaining material under tension in accordance with the presentinvention I utilize the tension impressed on the material as the drivingforce for a pump, and regulate'the condition under which the pumpoperates so as to make the power required -to drive the pump that whichwill put the "proper tension on the material. The fluid pumped may beeither a liquid or a gas, but preferably is the latter, and in practiceI ordinarily prefer to use an air pump or compressor of the positive.displacement type, and I regulate the pump driving force required bythrottling the outlet, or the inlet, or both outlet and inlet of thepump. In the case of web material drawn from a supply roll, the pump maybe driven either at a speed proportional to the speed of rotation of thesupply roll, or. proportional to the linear. speed of the web. Ingeneral when the ump is driven at. a speed proportional to t e speed ofthe web or strand, the controlling mechanism should operate to maintaina constant driving load on the supply roll or other tension controllingelement under the normal operating conditions. When the pump is drivenat a speed proportional to the speed of rotation of a supply roll orreel from which the web or strand is drawn, the braking load roll orreel is unwound and decreases in diameter and my invention comprisesprovisions for this purpose.

Heretofore various schemes have been proposed and some of them used, forautomatically controlling web or strand tension by exerting a brakingforce on a tension con trolling element, but thev present invention isdistinguished by the comparative r exerted by the pump should diminishas the.

simplicity and low cost of the apparatus required, the ease with whichit can be controlled and regulated in normal operation at full web orstrand speed, in starting, and in makin certain adjustments such as theinchlng adjustments necessary inthe operation of printing presses andother apparatus with which the invention may be used. The variousfeatures of novelty which characterize my'invention are pointed out withparticularity in the claims annexed to and forming a part of thisspecification. For a better understanding of the invention, however, andthe advantages possessed by it, and specific objects attained with itsuse, reference should bevhad to the accompanying drawings anddescriptive matter in which I have illustrated and described preferredmethods of and apparatus for carrying out my invention.

Of the drawings:

Fig. 1 is an elevation partly in section of apparatus comprising oneembodiment of my invention; v

Fig. 2 is a sectional elevation on a larger scalethan Fi 1 showing aportion of the apparatus of Fig. 1;

Figs. 3,4, 5, and 6 are diagrammatic elevations each of which representsa diiferent form of the invention;

Fig. 7 is a sectional elevation of a valve mechanism employed in Fig. 6;

Figs. 8 and 9 are elevations taken at right angles to one anotherillustrating another modification of the invention;

Fig. 10 is a sectional elevation of a portion of'the control valveemployed in Figs. 8 and 9;

Fig. 11 is a diagrammatic elevation of a slight niodification of theapparatus shown in F1gs., 8 and 9; and

Fig.12 is a diagrammatic representation of still another form of myinvention.

In thedrawings and referring firstto the apparatus shown in Figs. 1 and2, A represents the framework of a printing press or the like, providedwith bearings A for the spindle B of a supply roll B. The spindle Bcarries a spur gear B in mesh with a spur gear C journalled in theframework A at C. Preferably the parts are so arranged that the rollspindle B may be rolled along the framework guides A into the bearingsA, and so that as the spindle seats vitself, the gear B will come intomesh with the gear C. The gear C forms the driving element of thetension regulating pump which, in the construction shown, is areciprocating air compressor comprising two cylinders D set at rightangles to one another. The stems of the pistons D working in thecylinders D, are connected to crossheads D working in suitable guidewaysand connected by rods D to the same 0 "ant: pin C carried by the gear C.The cylinders D are each provided at each end with an inlet valve l1)and an outlet valve D The outlet valves D all. discharge into a pipingsystem E, preferably of small volumetric capacity, which opens to thein'let port F of the controlling valve F. The latter, as shown, isprovided with outlet ports F opening to the atmosphere. The port F iscontrolled by a poppet valve member F The stem of the valve member Fcomprises a cylindrical portion F" which works in a guideway or openngformed in the top of the valve casing. The upper end of the valve stemis threaded into one end of a turnbuckle adjusting device F. Into theopposite end of the turn-buckle is screwed a threaded projection F 7from a spring housing F \Vithin the spring hous ing F is a helicalspring F acting between the lower end of the spring housing and apiston-like follower F working in the housing F and secured to the lowerend of the rod F, which, as shown, is provided at its upper end with ananti-friction roll F engaged by a cam H. The latter is pivoted to thetlramework of the machine at H and is provided with an operating arm Hcarrying at its free end a roll H which bears against the periphery ofthe supply roll 13'. The cam is provided with a second arm H connectedby a spring H to the framework so as to lightly hold the roll H at alltimes in contact with the roll B.

In the normal contemplated mode of operation of the apparatus shown inFigs. 1 and 2, the web B of the paper or the like is drawn from thesupply roll B at a'rela tively high and more or less uniform speed bythe feeding mechanism, conventionally illustrated as rolls A, of themachine fed from the roll B. The pull thus exerted on the web B keepsthe roll B in rotation and thereby ope ates the compressor at a speedproportional to the speed of the rotation of the roll spindle B. Theforce required to drive the compressor, and the resultant braking orretarding force with which the compressor opposes the rotation of thesupply roll, depends primarily upon the differences between the fluidpressures at the inlet and outlet of the compressor, and with theapparatus shown in Figs. 1 and 2 this depends upon the tension of thevalve spring F. If the latter is of sufiicient length to make itstension substantially independent of the extent to which the valvemember F is open, the outlet pressure will be practically constant atall speeds and will be thatsat ficient to hold the valve F 01f its seat.On an increase or decrease in web speed, the valve F opens or closes asrequired to accommodate the resultant increase or decrease in fluiddelivery by the compressor Without appreciable change in the compressorde .livery pressure or in the web tension. A certain amount of power isrequired, of course, to overcome the friction losses in the compressor,but this power is comparatively constant and may be relatively smallwith suitably designed apparatus.

With a given linear speed of the Web B the angular velocity of the roll13' depends upon the amount of paper on the roll B, and increases as theamount of paper de* creases. In consequence the pressure against whichthe compressor discharges should decrease as the roll diameterdecreases, if a constant tension is to be maintained. This result isobtained with the apparatus shown in Figs. 1 and 2 by giving a suitablecontour to the cam H, so that as the roll decreases in diameter, thespring follower F is permitted to rise and thereby decrease the tensionwith which the spring F acts-on the valve disc F lVhile in general thetension on the web should remain constant as the roll diminishes indiameter, it is sometimes found desirable to decrease the web tensionwhen the supply rol'l is nearly all used up because irregularities thendeveloping in the contour of the supply roll tends to make the feedsomewhat irregular, and makes a reduced average tension desirable toavoid momentary increases in the web tension sufiicient to break theweb. This decrease in web tension when the roll becomes very small, canbe readily obtained by suitable shaping the cam H.

Among the advantages of regulating the tension by means of a pump asdescribed, is the simplicity and comparatively small cost of theapparatus required, the ease With which this apparatus may be installedin. connection with existing as well as new new printing presses, paperwaxing 1nachilies or other machines where a web or strand tensioncontrol is desirable; the reliability of operation of the apparatus; andthe ease with which it may be adjusted to meet changes in conditions ofoperation. For example, in handling paper, the tension of the web mayadvantageously be varied in some cases in response to changes in thehumidity of the atmosphere which affects both the flexibility andstrength of the paper web. Similarly different kinds of paper stock orvariations in the normal web speeds may make changes in web tensiondesirable. These changes in web tension are readily ob tainable with theapparatus shown, while the apparatus is in operation at full speed, by asimple adjustment of the turn-buckle I to correspondingly increase ordecrease the tension of the spring F An advantageous characteristic ofthe invention arises from the fact that at the instant of starting theapparatus into operation from a condition of rest, the pump imposes noinitial retarding force on the web except that due to friction. \Vhenthe comprcssor stops operation, the pressure at the outlet falls almostinstantly into'an equality with the pressure of the atmosphere as aresult of the inevitable leakage in the system. When the compressor isagain started into operation there is of course no resistance to itsOPOIzItlOD due to the excess of pressure at it outlet over that at itsinlet. The fact that the compressor thus exerts no resistance, asidefrom that due to frictional resistance, to the initial movement of theapparatus in starting is advantageous because the inertia of the supplyroll and the frictional resistance of the apparatus puts ample tensionon the web in starting. It will be understood, of course, that thefrictionalresistance to the rotation of the supply roll B and to theoperation of the compressor is greater in starting from rest than inrunning.

If the capacity of the piping E is small, as should ordinarily be thecase, only a small fraction of a turn of the roll B is required,however, to develop a pressure in the piping E which will put asubstantial tension on the web. This is largely desirable to avoid overtravel of the roll and conse uent festooning of the web in the so calledinching operation which, in the case of a printing press, for example,requires the web to be advanced a few inches at intervals in certainadjustments of the press.

With my improved tension regulating means, the tension maintained is adefinite function of the outlet pressure, and may be measured by meansof the pressure gauge S shown in Fig. 1 since my improved tensionregulator does not subject the web to undue tension in starting from acondition at rest and once started maintains practically constanttension at all speeds. The tension regulating means ordinarily does notrequire any adjustment in starting, running up to and at full speed andin slowing down and stopping. This fact, coupled with the fact that thetension maintained is a definite and easily determined thing makes itreadily possible to run the web with less tension than is ordinarilyemployed with heretofore used tension devices with which the actualtension maintained is not readily known and which require adjustment instarting up or slowing down. lVith such tension devices the tensionactually employed is usuall more than in really necessary to insuresufl'i cient tension. Excess tension is objectionable because itinvolves extra driving power unnecessarily large Wear due to friction,as well as increased frequency of Web rupture.

. In the modification illustrated in Fig. 3, l

the reduction in the compressor outlet pressure to compensate for-thedecrease in diameter of the roll B as the latter is unwound, is madedirectly dependent on the weight of the roll B. For this purpose theroll B is mounted in arms AA pivoted to turn about an axis coaxial withthe. shaft C of the compressor driving gear 0, and the weight of theroll B and of the arms AA is carried by helical springs A" so that theroll spindle B rises and falls with the changes of weight of the webmaterial wound about it. As shown one of the arms AA directly engagesthe anti-friction roller F ofa control valve F, which may be identicalwith that shown in Figs. 1 and 2. The valve F thus tends to decrease thecompressor outlet pressure as the weight of the roll B di minishes. Thesame variation in throttling eifect may be obtained by difierences inshape and disposition of the portion of the arm AA engaging the roll Fas is obtainable in the construction shown in Figs. 1 and 2 by varyingthe contour of the cam H.

In Fig. 4 l have illustrated a modification of the invention whichdiffers from that shown in Figs. 1 and 2 only in that the throttlingvalve F is adjusted in direct response to. the tension 011 the web B.For

this purpose I replace the cam H of Figs. 1

and 2 by a cam I journalled at I, and connected to an arm 1 carrying anidler roll I which rests on the portion of the Web B" running from theroll B to an adjacent guide or feed roll A. With this arrangement thetension on the portion of the web engaged'by the roll I will be afunction of, and will be measured by the elevation at which the roll Iis held. On a decrease or increase in the tension ofthe portion of theweb engaged by the roll 1*, the latter will fall or raise and thusincrease or decrease the tension of the spring F of the regulating valveF.

In Fig. 5 I have illustrated a modification of the apparatus shown inFig. 1 in which the compressor outlet pressure is automaticallyregulated in direct response to the speed of operation of the apparatus.As s 10WI1 in Fig. 5. the throttling effect on the compressor outlet isvaried in response to changes in the speed of rotation of the rollspindle B by means of a valve FA controlling the discharge into theatmosphere from the piping E through a branch discharge pipe E. Themovable valve member F of the valve FA has its stem F" connected to theaxially movable element of a ball governor KA which is driven from theroll spindle B and carried by the spindle B by means of a shaft K, abevel gear B, and a meshing bevel gear K carried by the shaft K. Asshown the valve member F isprovided with a cylindrical skirt havinnotches F the shape of which determines the effective free port area indifferent positions of the valve members. B suitab y shaping the notchesF the bralting effect of the compressor can be varied to compensate forchanges in the diameter of the roll B as is done with the apparatus ofFigs. 1 and 2 by varying the contour of the cam H. To provide for afurther adjustment of the braking eil'ect of the compressor in directresponse to the speed of the web 13, I employ in Fig. 5 a supplementalregulating valve FB which may be generally similar to the valve FA,which may well be rectangular in the valve FE and V-shaped in the valveFA. The stem F" of the valve FB is connected to the axially movablemember of a ball governor KB which is driven at a speed proportional tothe speed of the web, this result being obtained in the arrangementshown in Fig. 5 by gearing the governor KB to one of the feed rolls AThe valve F B discharges air into the atmosphere from the piping Ethrough the branch outlet pipe E While in the forms of my inventionheretofore described I have employed a braking compressor of thereciprocating type, 1t Wlll be understood, of course, that other typesof compressors may be employed, and indeed I prefer ordinarily to employa rotary compressor of the well known positive displacement type such asthe well known compressor illustrated in Fig. 6 in which the compressordriving gear C is mounted on the shaft of the rotary compressor DA. Thecontrol valve mechanism employed with the apparatus shown in Fig. 6 maybe identical with that shown in Fig. 2 but the valve mechanism FC shownin Fig. 6 and in Fig. 7 is of a modified form.

The valve FC comprises an inlet chamber F and an outlet chamber'F. Theinlet chamber F is connected to the outlet port of the compressor bypiping E which is preferably short and of small volumetric capacity. Thechambers F and F are I connected by a port F directly controlled by amovable valve member F The outlet chamber F is connected to a smallpressure equalizing reservoir G and opens to the atmosphere inoperation, through ports F controlled by a cylindrical valve member Fsecured to the valve member F and .preferably of larger diameter thanthe latter. The valve members F and F are rigidly connected to a guidemember F 4 and are urged toward their closed positions by a spring Fworking in a housing F and interposed between the guide F and a followerF connected by the turn-buckle F and adjustable extension F carrying ananti-friction roll F engaged by a cam H as in Fig. 1. The valve membersF and F are so shaped that the ports F are fully covered until after theinitial upward movement of the valve members. The small volumetriccapacity preferably provided between the compressor outlet proper andthe port F facilitates a quick building up of the tension creating dragof the compressor as the latter starts into operation. This quickbuilding up of a substantial tension in starting may be augmented, asshown, by making the portion of the valve member exposed to the pressurein the compressor outlet before the valve member moves to open port Fsmaller than the portion exposed after the port F is opened.

The reservoir G serves to equalize the compressor discharge pressure,and substantially eliminate all tendency of the valve to chatter. At thesame time its location prevents it from retarding the rate at which thecompressor outlet pressure builds up in starting.

Instead of driving the braking compressor by positive gearing betweenthe supply roll spindle and the compressor as shown in the forms inFigs. 1, 3, 4, 5 and 6, I may, advan tageously, in some cases, drive thecompressor through a belt or pulley bearing against the periphery of thepaper roll. Thus in the arrangement shown in Figs. 8 and 9. the rotarycompressor DA has driving pulleys D secured to the ends of thecompressor shaft. Each of the pulleys D is connected by a belt D to anidler pulley D journalled at the end of a corresponding arm D shown aspivotally connected to the housing of the compressor DA, and normallyurged by its own weight and by an adjustable loading weight D againstthe periphcry of the roll B. As shown each weight D is carried by aprojection D from the corresponding arm D and the parts are so shapedand disposed that as the arm D turns about its pivotal support tomaintain the belt D in contact with the roll B as the latter is unwoundand decreases in diameter the contact pressure between the belt Dand-the roll B will remain approxi mately constant and prevent slippageas the roll decreases in diameter and the arm 'A swings downward fromits initial position. Since with the type of apparatus shown in Figs. 8and 9 the speed of the compressor is proportional to the speed of theweb regardless of the diameter of the roll B, the controlling valvemechanism FD need not include provisions for automatic adjustment inresponse to the change in the ratio between the web speed and theangular velocity of the roll. The valve FD may be and is shown as beingsimilar to the valve FC except that the follower F (see Fig. 10) iscarried by a screw spindle which is threaded through the end of thespring Inc housing F and provided at its outer end with a hand wheel F.By rotating the hand wheel F adjustments of the tension of the spring Fmay be obtained analogous to those obtained with the valves F and FC byadjustments of the turn-buckles F. The purpose of providing two drivingbelts I with the compressor DA shown in Figs. 8 and 9 is to obtain thenecessary amount of driving effort in handling webs of full width,without requiring unnecessary friction when a half length roll is usedas is sometimes the case in printing presses. In such case one of thebelts D may be removed or permitted to run idle.

In Fig. 11 I have illustrated a modification of the apparatus shown inFigs. 8 and9 in which the arms D each has journalled at its free end afriction roll D which bears against the periphery of the supply roll andis connected by a driving chain or belt D to a pulley D replacing thecorresponding pulley D of the apparatus shown in Figs.-

8 and 9.

While I prefer that the fluid pumped by my tension regulating pumpshould be an elastic fluid such as air, this fluid may be a liquid suchas water or oil in which case the pump should be connected to acirculating system into which the pump discharges and from which thecontrolling liquid is returned to the pump inlet. In Fig. 12 I havediagrammatically illustrated a system of this sort in which DBrepresents the regulating pump which may be either a reciprocating pumpor a rotating pump and if the latter as is shown in Fig. 12, the pump ispreferably of the positive displacement type, though a centrifugal pumpmay be employed. In the particular arrangement shown in Fig. 12, thepump DB is driven from the roll B by power transmitting means similar tothose shown in Figs. 8 and 9, and the pressure at the pump outletregulated by a valve FD which may be like the valve FD employed in Figs.8 and 9 except that the connection to the pressure equalizing chamber Gof the valve mechanism shown in Figs. 8 and 9 is omitted. As shown anair containing pressure equalizing chamber GAis connected to outlet pipebe tween the pump outlet F and the valve FD. The liquid discharged fromthe pump outlet F passes into a tank or reservoir R from which liquidpasses by gravity to the pump inlet D Special features of constructionand ar--' rangement diflerentiating the .forms of my inventionillustrated'in Figst8, 9, 11 and 12 from other forms of my inventionherein illustrated are claimed in my co-pending application, Serial No.508548, 'Pat. No. 1,538,887, filed of even date herewith.

While in accordance with the provisions of the statutes I haveillustrated and described the best forms of my invention now known tome, it will be understood that changes in the form of the apparatus andmethods of operation specifically disclosed herein may be made withoutdeparting from the spirit of my invention as set forth in the appendedclaims, and that some of the features of my invention may sometimes beused to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and. desire tosecure by Letters Patent, is: s

1. The method of subjecting web or strand-like material to tension whilesaid material is travelling at varying speeds which consists inoperating a pump by a driving force transmitted to the pump through thematerial and variably throttling the pump outlet as required to maintainan approximately constant tension with varying pump speeds by opposingthe outflow through said outlet with a resilient force of regulableintensity.

2. The method of regulating the tension on a web being unwound from asupply roll which consists in gearing the supply roll spindle to a pumpand varying the pressure differential between the pump inlet and thepump outlet in automatic response to the amount of material on thesupply roll to compensate for the reduction in diameter of the roll asthe latter is unwound by opposing the outflow through said outlet with aresilient force, the intensity of which is automatically diminished asthe diameter of the roll increases.

3. The combination with means for advancing web or strand-like material,of means for regulating the tension to which the material is subjectedcomprising a pump and means for driving the pump by force transmittedthrough the material from the means for advancing the material and meansfor maintaining an approximately constant pump delivery pressurenotwithstanding variations in the pump speed comprising a valve membersubjected to the opposing action of the outlet pressure and of aregulable tension controlling force.

4. The combination with means for advancing web or strand-like material,of a pump driven by the web at a speed which is a function of the speedat which the web is advanced, and a valve regulating the pressure at theoutlet of the pump comprising a valve member subjected to the opposingaction of the outlet pressure and of a regulable tension controllingforce. I 1

5. The combination with a supply roll comprising a spindle about whichmaterial is wound, of means for drawing the material from the supplyroll and means for regulating the tension of the material comprising a.pump connected to and driven by said spindle, a valve regulating thepump dischargeand subjected to the opposing action of the pump deliverypressure tending to open the valve and a regulable tension controllingl'orce tending to close the valve and means for diminishing said forceas the roll decreases in diameter.

(3. The combination with a supply roll comprising a spindle about whichmaterial is Wound of means for drawing the material from the supply rolland a pump connected to and driven by said spindle, a valve regulatingthe pump delivery pressure comprising a valve member acted on by thepump delivery pressure in a direction tending to open the valve andthereby decrease the pump delivery pressure and subjected to the actionof a tension spring tending to close the valve and means for adjustingthe tension of said spring in automatic response to changes in thediameter of the supply roll.

Signed at New York, in the county of New York and State of New York,this 17th day of October, A. D. 1921.

CHARLES E. CARPENTER.

